The Abbott government has opened up another front in its war on renewable energy by pulling the plug on investments in the most common form of alternative energy, rooftop and small-scale solar.

As a storm raged over the government's directive to the Clean Energy Finance Corporation to no longer back wind energy projects, it emerged that it has also put a stop to solar investments other than the largest industrial-scale projects.

The solar industry has been left fuming by a letter to the CEFC by Treasurer Joe Hockey and Finance Minister Mathias Cormann in which they direct investments in household and small-scale solar to be "excluded" from the $10 billion fund in future.

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The draft investment mandate calls for "mature and established clean energy technologies … to be excluded from the corporation's activities, including extant wind technology and household and small-scale solar".

Currently, about a third of all CEFC investments involve small-scale solar. The corporation, which has produced more than a $1 profit for the government for every $1 invested, was assessing $500 million in finance for solar projects valued at more than $1 billion.

There are 1.3 million rooftop solar systems in Australia and most households receive publicly-backed rebates to install, but the CEFC has made a priority projects that help people who do not own their own homes, those who live in apartments and community groups to invest in solar panels.

This month, a $100 million deal between the profit-making corporation Origin Energy to facilitate solar take up was announced.

The CEFC would not comment on Sunday but solar industry leaders have become aware of the contents of Mr Hockey and Senator Cormann's letter.

Joe Hockey says it's important for a government to 'get your house in order'.Credit:Jerome Favre

Australian Solar Council chief executive John Grimes accused Tony Abbott of playing "cynical politics" after the Prime Minister insisted on Sunday that his government "supports renewables" but wants to "reduce the upward pressure on power prices".

Mr Grimes said the CEFC had made it possible for low-income people and retirees to invest in solar and take advantage of the power bill savings that flow.

The government tried and failed to abolish the profit-making CEFC after failing to get Senate support and its latest strike against wind and solar is expected to further scare renewable energy investors away from Australia, Labor and the Greens claim.

"While the CEFC exists, what we believe it should be doing is investing in new and emerging technologies, certainly not existing wind farms," Mr Abbott said.

In a letter to Mr Hockey and Mr Cormann in February, CEFC chairwoman Jillian Broadbent pointed out that the act governing the corporation compelled it to "facilitate increased flows of finance into the clean energy sector" rather than only pursue emerging technologies.

A copy of the latest investment mandate from the government in March does not specify anything about not investing in established renewable, only that the CEFC should "help mobilise investment in renewable energy, low-emissions and energy efficiency projects".

The CEFC website states its investment focus as being on projects at the "later stages of development which have a positive expected rate of return and have the capacity to service and repay capital." The CEFC Act currently only excludes investment in carbon capture and storage, nuclear technology or nuclear power.